:* Explain Define the purpose of term '''Regular Expressions'''

:* Understand Explain the difference between '''Regular Expressions ''' and '''Filename Expansion'''

:* Understand Explain the purpose of '''Literal (Simple) ''' Regular Expressions

:* Understand and use common symbols for '''Complex ''' Regular Expressions and their purpose

:* Understand and use command symbols for '''Extended ''' Regular Expressions and their purpose

:* Use various List several Linux commands that can use regular expressions<br>

|colspan="2" |Course Notes'''Slides:'''<ul><li>Week 9 Lecture 1 Notes:<br>[https://ictwiki.cdot.senecacollege.ca/~murrayuli101/slides/ULI101-9.1.pdf PDF] | [https://wiki.saulcdot.senecacollege.ca/uli101/slides/ULI101-Week99.1.pptx PPTX]</li><li>Week 9 Lecture 2 Notes:<br> [https://wiki.cdot.senecacollege.ca/uli101/slides/ULI101-9.2.pdf PDF] | [https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101slides/ULI101-Week99.2.pptx PPTX]<br></li></ul>

| style="padding-left:15px;" |'''Regular Expressions:'''* Simple[https://techterms.com/definition/regular_expression#:~:text=A%20regular%20expression%20(or%20%22regex,wildcards%2C%20and%20ranges%20of%20characters.&text=A%20regular%20expression%20can%20be,%2C%20such%20as%20%22app%22. Definition]* Complex* Extended[https://en.wikipedia.org/wiki/Regular_expression#:~:text=Regular%20expressions%20are%20used%20in,built%2Din%20or%20via%20libraries. Purpose (WIKI)]<br><br>

| style="padding-left:15px;"|Additional '''Linux Commands that Use Regular Expressions:'''* [https://ss64.com/bash/egrep.html egrep]

|colspan="1" style="padding-left:15px;" width="30%"|'''Brauer Instructional Videos:'''<ul><li>[https://www.youtube.com/watch?v=-2pwLHcvCsU&list=PLU1b1f-2Oe90TuYfifnWulINjMv_Wr16N&index=12 Using grep Command with Regular Expressions]</li></ul>

A '''regular expression''' … is a sequence of characters that define a search pattern.  Usually such patterns are used by string searching algorithms for "find" or "find and replace" operations on strings, or for input validation. <br>Reference: https://en.wikipedia.org/wiki/Regular_expression ===Regular Expressions vs. Filename Expansion===

<table align="right"i><tr valign="top"><td>[[ImageA '''regular expression''' is a combination of two types of characters:re-1.png|thumb|right|350px|Filename expansion symbols allow the Linux shell to expand filenames as arguments (referred to as “globbing”).]]</td><td>[[Image:re-2.png|thumb|right|250px|Output of the '''ls -lRliterals''' and '''special characters''' command to display directory structure.]]</tdbr></table>In a previous lesson, you learned that filename expansion symbols allow the Linux shell Strings of text can be compared to expand filenames as arguments (referred this pattern to as “globbing”) for file management commands. This see if there is very useful for managing multiple files sharing similar characteristics such as the same file extensiona match. </i>

Filename Expansion symbols are used This usually refers to search, edit and manipulate text and are used with Linux file management commands such as that is <u>contained</u> inside a '''ls''', '''rm''', '''mv''', '''cp''', '''cat''', '''less''' and ''file'more'''. This can represent text contained in files or text as a result <br>of issuing Linux commands using a pipeline. A '''regular expression''' is a combination of two types of characters: '''literals''' and '''special charactersLinux pipeline command'''.<br>In combination, these characters define a logical pattern. Strings of text can be compared to this pattern<br>to see if they fit the pattern defined by the expression. Reference: https://www.whoishostingthis.com/resources/regex/

[[Image:re-3.png|thumb|right|250px200px|The simplest A '''simple''' ('''literal''') regular expression is a series of letters and numbers, possibly including white space (tabs or space charactersspaces).]]The simplest regular expression is a series of letters and numbers, possibly including white space (tabs or space charactersspaces), that have no special meaning. Such a <br>A '''simple''' ('''literal''') regular expression consists of ``literals''; that is, normal letterscharacters, which used to match only an identical letter in the data being searchedpatterns.<br><br>For example:"This is a regular expression"<br><br>When an editor searches for a literal regular expression, it can only score a ``hit'' if it finds exactly Although there are many Linux commands that sequence of characters in the data it is searching. <br>Reference: http://osr507doc.xinuos.com/en/OSUserG/_Literal_chars_in_regexps.html ===Complex Regular Expressions=== The problem with using literals or simple use regular expressions is that general patterns are matched.  For example, the pattern “'''the'''” would be matched for larger word containing that pattern like '''there''', '''they''', '''either''', '''them''', '''theirgrep''', etc. Another problem command is that you may want a useful command to learn how to search for pattern at a specific location display matches of patterns of strings within the string of text (like at the beginning or end)files.<br><br>For example:<span style="color:blue;font-weight:bold;font-family:courier;">grep Linux document.txt</span><br><br>

'''Complex Regular Expressions use symbols to help match text for more precise or complex patterns.'''<br><br>The most common complex problem with just using '''simple''' ('''literal''') regular expression symbols expressions is that only <u>simple</u> or <u>general</u> patterns are displayed below:matched.

:*''Complex Regular Expressions'Anchors'use symbols to help match text for more <u>precise</u> (complex) patterns.<br>The most common complex regular expression symbols are displayed below:<br><br>:'' 'Anchors: '''<span style="color:blue;font-family:courier;font-weight:bold;">^''' </span> , '''<span style="color:blue;font-family:courier;font-weight:bold;">$</span><br>Match lines the begin (^) or end ($) with a pattern.<br>:'''Single Character:*'''Characters &nbsp; <span style="color:blue;font-family:courier;font-weight:bold;">.'''</span><br>Represents a single character that can be any type of character.<br>:*'''Character Class [ ]:''' <span style="color:blue;font-family:courier;font-weight:bold;">[ ]</span> , '''<span style="color:blue;font-family:courier;font-weight:bold;">[^ ]'''</span><br>Represents a single character but with restrictions.<br>:*'''Zero or More Occurrence *:''' <span style="color:blue;font-family:courier;font-weight:bold;">*</span><br>Zero or more occurrences of previous character.<br><br>

:Examples of how to use these '''complex regular expressions with the grep command ''' are displayed below:

<table align="left"><tr valign="top"><td>[[Image:re-4.png|thumb|right|220px200px|Example of using '''anchors'''.]]</td><td>[[Image:re-5.png|thumb|right|200px175px|Example of matching charactersby '''character(s)'''.]]</td><td>[[Image:re-6.png|thumb|right|220px|Example of using '''character class'''.]]</td><td>[[Image:re-7.png|thumb|right|200px|Example of matching '''zero or more occurrenceof preceding character'''.]]</td></tr></table><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>

'''Extended Regular Expressions consist of additional special characters the “extend” the capability of regular expressions.'''

''Extended Regular Expressions'Repetition {min,max}''' , consist of additional special characters to “extend”<br>the capability of regular expressions. You must use the '''?egrep''' , or '''+grep -E'''commands<br>Allows for more precise repetitions. Using braces, you can specify the minimum and maximum number of repetitionsin order to properly use extended regular expressions.

:'''Grouping ( )Repetition:'''<span style="color:blue;font-family:courier;font-weight:bold;">{min,max}</span><br>Perhaps you want to search Allows for repetition for a group of charactersmore precise repetitions. Using braces, a word, or a phase.you can specify<br>You can enclose them within brackets ( ) to specify a groupthe '''minimum''' and/or '''maximum''' number of repetitions.

:'''or Condition |:''' <span style="color:blue;font-family:courier;font-weight:bold;">|</span><br>Can be used with grouping '''groups''' to match a variety of character(s), words or phases. <br>The | symbol is used to separate the variety of character(s)within a ''group''.<br><br>

:Examples of how to use these complex '''extended regular expressions ''' with the grep '''egrep''' command are displayed below:<br><br>

<table align="left"><tr valign="top"><td>[[Image:re-8.png|thumb|right|280px|Example of using '''repetition'''.]]</td><td>[[Image:re-9.png|thumb|right|250px|Example of using grouping'''groups'''.]]</td><td>[[Image:re-10.png|thumb|right|250px|Example of using '''or ''' condition with grouping'''groups'''.]]</td></tr></table>

<span style="color:red;">'''ATTENTION''': This online tutorial will be required to be completed by '''Friday in week 10 by midnight''' to obtain a grade of '''2%''' towards this course</span><br><br> In this sectioninvestigation, you will learn how to use the '''grep ''' command with '''simple and complex regular expressions '''<br>to help search for ''patterns '' contained in text files.

# '''Login''' to your matrix account.<br><br># Issue a Linux command to '''confirm''' you are located in your '''home ''' directory.<br><br>The # Issue the following linux Linux command to '''wgetcopy''' command is used to download files from the Internet a text file to ''your shell.'' '''home''' directory from the ULI101 home directory:<br>This will be useful to download text files that we will be using for this tutorial.<br><br># Issue the following linux command ('''copy and paste''' to save time):<br><span style=span style="color:blue;font-weight:bold;font-family:courier;">wget <nowiki>https:cp ~uli101//ict.senecacollege.ca/~murray.saul/uli101tutorialfiles/textfile1.txt<~/nowiki></span><br><br># Issue View the contents of the '''lstextfile1.txt''' command to confirm that file using the text file was downloaded'''more''' command see what data is contained in this file.<br><br># View the contents of Although there are several Linux commands that use regular expressions,<br>we will be using the '''textfile1.txt''' file using the '''moregrep''' command and quickly view the contents of for this file. When finished, exit the more commandinvestigation.<br><br>Although there are several Linux commands that use regular expressions, we will only be using the [[Image:regexps-1.png|thumb|right|250px|Output of '''grep ''' command for this section.<br><br>#Issue the following linux pipeline command to match the pattern the within matching simple regular expression "'''textfile1.txtthe''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "(only lowercase). Notice thepattern matches larger words like "'''their'''" or " textfile1.txt | more<br><br># Now, issue the grep linux pipeline command with the '''-ithem'''".]]#Issue the following Linux command to match the pattern '''the''' within '''textfile1.txt''' option to ignore case sensitively:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -i "the" textfile1.txt | more</span><br><br>What do you notice is different with this pipeline command?Take a few moments to view the output and observe the matched patterns.<br><br>You will notice that # Issue the pattern "grep Linux command with the<span style=" is matched including larger words that contain the pattern font-weight:bold;font-family:courier;"the". You can use the >-w i</span> option with the grep command in order to just match only words for a pattern.ignore case sensitively:<br><br># Issue the following linux pipeline command:<br><span style="color:span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "the" textfile1.txt | more</span><br><br>What do you notice is different when issuing this command?<br><br>You should now see only strings of text will notice that match the word pattern "'''the'''"theis matched including larger words like "'''them'''" and "'''their'''".<br><br>Just matching literal or simple regular expressions can be useful, but are limited in what they can assist with pattern matching.<br>For Example, you may want to search for pattern at a specific location within You can issue the string of text (like at '''grep''' command with the beginning or end of the string).<br<span style="font-weight:bold;font-family:courier;">-w<br/span>There are other regular expression tools option to provide more precise matches. These tools are only match the pattern as a '''complex''' and ''word'extended''' regular expressions. We will now look at complex regular expression symbols now, and we will discuss ''extended regular expressions''''''Italic text'''' in <br><br># Issue the next section of this tutorial.<br><br># Issue the following Linux pipeline commandfollowing Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^the" textfile1.txt | more</span><br><br>The You should now see only strings of text that match the word '''^the''' symbol is an anchor. In this case, it only matches the <u>word</u> "the" (both upper or lowercaselower case) at the beginning of strings.<br>The <br>Matching literal or simple regular expressions can be useful, but are '''$limited''' symbol is used to anchor patterns at the end of strings.<br>in what pattens they can match. For example, you may want to<br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;"search for a pattern located at the '''beginning''' or '''end''' of the string.<br>grep -w -i "the$" textfile1.txt | more</span><<br>There are other regular expression symbols that provide more '''precise''' search pattern matching.<br>What do you notice?<br><br># Issue the following Linux pipeline command to anchor the work "the" simultaneously at the beginning and the end of the string:These special characters are known as '''complex''' and '''extended''' regular expressions symbols.<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^br>For the$" textfile1.txt | more</span>remainder of this investigation, we will focus on '''complex regular expressions''' and then<br>focus on ''extended regular expressions'' in INVESTIGATION 2.<br>What do you notice?<br><brtable align="right">Anchoring patterns at both the <utr valign="top">beginning</u> and <u>ending</utd> [[Image:regexps-2.png|thumb|right|280px|Anchoring regular expressions at the '''beginning''' of strings can greatly assist for more complex search patternstext.]]<br/td><td>We will now be demonstrating simultaneous anchoring with other complex [[Image:regexps-3.png|thumb|right|250px|Anchoring regular expressions symbolsat the '''ending''' of text.]]<br/td><br/tr></table># Issue the following Linux command to match strings that begin with 3 characters:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^...the" textfile1.txt | more</span><br><br>What do you notice?<The '''^''' symbol is referred to as an '''anchor'''.<br>In this case, it only matches<br># Issue the following command to match strings that begin and end with 3 characters:word "'''the'''" (both upper or lowercase) at the <u>beginning</u> of the string.<br><br># Issue the following Linux command:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "^...the$" textfile1.txt | more</span><br><br>What do you notice?<The '''$''' symbol is used to anchor patterns at the <u>end</u> of the string.<br><br># Issue the following Linux command to match strings that begin with 3 digits:anchor the <bru>word<span style=/u> "color:blue;font-weight:bold;font-family:courier;'''the'''"<br>grep "^[0-9][0-9][0-9]" textfile1.txt | more'''simultaneously''' at the </spanu>beginning<br/u>and <bru>end</u># Issue of the following command to match strings that end with 3 uppercase lettersstring:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep -w -i "[A-Z][A-Z][A-Z]$^the$" textfile1.txt | more</span><br><br># Issue What do you notice?<br><br>Anchoring patterns at both the following command to match <u>beginning</u> and <u>ending</u> of strings that consist of only 3 digits:can greatly assist<br><span style="color:blue;font-weight:bold;font-family:courier;"for more '''precise''' search pattern matching.<br><br>We will now be demonstrate the '''effectiveness''' of <u>grep "^^[0-9][0-9][0-9]$" textfile1.txt | morecombining</spanu><br>'''anchors''' with <u>other</u> complex regular expressions symbols.<br><br><table align="right"><tr valign="top"><td>[[Image:regexps-4.png|thumb|right|280px|Anchoring regular expressions using '''period''' symbols at the '''beginning''' of text.]]</td><td>[[Image:regexps-5.png|thumb|right|250px|Anchoring regular expressions using '''period''' symbols simultaneously at the '''beginning''' and '''ending''' of text.]]</td></tr></table># Issue the following Linux command to match strings that '''begin with 3 characters''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^..." textfile1.txt</span><br><br>What do you notice? Can lines that contain '''less than 3 characters''' be displayed?<br><br># Issue the following Linux command to match strings that '''begin <u>and</u> end with 3 characters''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^...$" textfile1.txt</span><br><br>What do you notice compared to the previous command?<br><br># Issue the following Linux command to match strings that '''begin with 3 digits''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9][0-9][0-9]" textfile1.txt</span><br><br>What did you notice?<br><br># Issue the following Linux command to match strings that '''end with 3 uppercase letters''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "[A-Z][A-Z][A-Z]$" textfile1.txt</span><br><br><table align="right"><tr valign="top"><td>[[Image:regexps-6.png|thumb|right|220px|Anchoring '''3 digits''' at the '''beginning''' and '''ending''' of text.]]</td><td>[[Image:regexps-7.png|thumb|right|250px|Anchoring '''3 alpha-numeric characters''' at the '''beginning''' and '''ending''' of text.]]</td></tr></table>What type of strings match this pattern?<br><br># Issue the following Linux command to match strings that '''consist of only 3 digits''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9][0-9][0-9]$" textfile1.txt</span><br><br>What did you notice?<br><br># Issue the following Linux command to match strings that '''consist of only 3 alphanumeric digits''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9]$" textfile1.txt</span><br><br>What did you notice?<br><br>The <span style="font-weight:bold;font-family:courier;">"*"</span> complex regular expression symbol is often confused with the "*" '''filename expansion''' symbol.<br>In other words, it does NOT represent zero or more of '''any character''', but zero or more '''occurrences'''<br>of the character that comes '''before''' the <span style="font-weight:bold;font-family:courier;">"*"</span> symbol.<br><br># To demonstrate, issue the following Linux command to display '''zero or more occurrences''' of the letter "'''x'''":<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "x*" textfile1.txt</span><br><br>You will most likely notice most lines of the file is displayed.<br><br># Let's issue a Linux command to display strings that contain '''more than one occurrence''' of the letter "'''x'''":<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "xx*" textfile1.txt</span><br><br>Why did this work? because the pattern indicates one occurrence of the letter "x",<br>followed by '''zero or MORE occurrences''' of the <u>next</u> letter "x".<br><br>If you combine the complex regular expression symbols <span style="font-weight:bold;font-family:courier;">".*"</span> it will act like<br>zero or more occurrences of <u>any</u> character (i.e. like <span style="font-weight:bold;font-family:courier;">"*"</span> did in filename expansion).<br><br># Issue the following Linux command to match strings begin and end with a number with nothing or anything inbetween:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9].*[0-9]$" textfile1.txt</span><br><br>Using '''simultaneous anchors''' combined with the <span style="font-weight:bold;font-family:courier;">".*"</span> symbol(s) can help you to refine your search patterns of strings.<br><br># Issue the following Linux command to display strings that begin with a capital letter,<br>end with a number, and contains a capital X somewhere inbetween:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[A-Z].*X.*[0-9]$" textfile1.txt</span><br><br>Let's look at another series of examples involving searching for strings that only contain '''valid numbers'''.<br>We will use '''pipeline commands''' to both display stdout to the screen and save to files<br>for confirmation of running these pipeline commands when run a '''checking-script''' later in this investigation.<br><br># Issue the following Linux command to create the '''regexps''' directory: <span style="color:blue;font-weight:bold;font-family:courier;">mkdir ~/regexps</span><br><br># Change to the '''regexps''' directory and confirm that you have moved to this directory.<br><br># First, issue the following Linux command to copy another data file called '''numbers1.dat''':<br><span style="color:blue;font-weight:bold;font-family:courier;">cp ~uli101/tutorialfiles/numbers1.dat ~/regexps</span><br><br># View the contents of the '''numbers.dat''' file using the '''more''' command and quickly view the contents of this file.<br>You should notice '''valid''' and '''invalid''' numbers contained in this file. When finished, exit the more command.<br><br># Issue the following linux pipeline command to display only '''whole''' numbers (i.e. no '''+''' or '''-''' sign):<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9]*$" numbers1.dat | tee faulty.txt</span><br><br>You may have noticed that the command '''does not entirely work'''. You may notice an '''empty line'''<br>(which is NOT a whole number). This occurs since the * regular expression symbol represents<br>ZERO or MORE occurrences of a number. You can use an additional numeric character class<br>with the * regular expression symbol to search for one or more occurrences of a number.<br><br># Issue the following Linux pipeline command to display only whole numbers:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[0-9][0-9]*$" numbers1.dat | tee whole.txt</span><br><br>You should see that this now works.<br><br># Issue the following Linux pipeline command to display <u>only</u> '''signed''' integers:<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-][0-9][0-9]*$" numbers1.dat | tee signed.txt</span><br><br>What did you notice? Positive and negative numbers display, not '''unsigned''' numbers.<br><br>[[Image:regexps-8.png|thumb|right|300px|Simultaneous '''anchoring''' of regular expressions using '''character class''' and '''zero or more occurrences''' to display '''signed''' and '''unsigned''' integers.]]# Issue the following Linux pipeline command to display '''signed''' or '''unsigned integers''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-]*[0-9][0-9]*$" numbers1.dat | tee all.txt</span><br><br>Did this command work?<br><br># Issue the following command to check that you created those hard links: <br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week9-check-1</span><br><br>If you encounter errors, then view the feedback to make corrections, and then re-run the checking script. If you receive a congratulation message that there are no errors, then proceed with this tutorial.<br><br>You can also use the '''grep''' command using ''regular expression'' as a '''filter''' in pipeline commands.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | grep "[0-9].*dat$"</span><br><br>What did this pipeline display?<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | grep "[a-z].*txt$"</span><br><br>What did this pipeline display?<br><br> : Although very useful, '''complex''' regular expressions do NOT <u>entirely</u> solve our problem of displaying<br> '''valid''' unsigned and signed numbers (not to mention displaying decimal numbers).<br><br>In the next investigation, you will learn how to use '''extended''' regular expressions that will completely solve this issue.<br> : You can proceed to INVESTIGATION 2.<br>

<br>In this sectioninvestigation, you will learn how to use '''extended regular expressions''' with the '''egrep''' command<br>to further refine your search patterns... 

# xMake certain that you are located in your '''~/regexps''' directory on your ''Matrix'' account.<br><br># Issue the following Linux command to copy another data file called '''numbers2.dat''':<br><span style="color:blue;font-weight:bold;font-family:courier;">cp ~uli101/tutorialfiles/numbers2.dat ~/</span><br><br># View the contents of the '''numbers2.dat''' file using the '''more''' command and quickly view the contents of this file.<br>You should notice ''valid'' and ''invalid'' numbers contained in this file. When finished, exit the more command.<br><br>[[Image:eregexps-1.png|thumb|right|300px|'''Weakness''' of '''complex''' regular expressions that do not '''limit''' the number of '''positive''' or '''negative''' signs.]]# Issue the following Linux command to display '''signed''' or '''unsigned integers''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-]*[0-9][0-9]*$" numbers2.dat</span><br><br>You should notice '''multiple''' '''+''' or '''-''' '''signs''' appear <u>prior</u> to some numbers.<br>This occurs since you are searching or one or MORE occurrences of a + or - sign.<br><br>Using '''extended regular expression''' symbols to specify '''minimum''' and '''maximum''' repetitions: '''{min,max}''' can solve that problem.<br><br># Issue the following Linux command (using extended regular expression symbols)<br>to display '''signed''' or '''unsigned integers''':<br><span style="color:blue;font-weight:bold;font-family:courier;">grep "^[+-]{0,1}[0-9]{1,}$" numbers2.dat</span><br><br>'''NOTE: No output will be displayed! Why?'''<br><br>This is due to the fact that the '''grep command was NOT issued correctly to use extended regular expression symbols'''.<br>You would need to issue either '''grep -E''', or just issue the '''egrep''' command. The egrep command works with<br>'''all''' regular expression symbols, and should be used in the future <u>instead</u> of the older grep command.<br><br>We will use '''pipeline commands''' to both display stdout to the screen and save to files<br>for confirmation of running these pipeline commands when run a '''checking-script''' later in this investigation.<br><br># Issue the following Linux pipeline command using '''egrep''' instead of ''grep'':<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep "^[+-]{0,1}[0-9]{1,}$" numbers2.dat | tee better-number1.txt</span><br><br>[[Image:eregexps-2.png|thumb|right|300px|Using '''extended''' regular expression symbols (such as '''repetition''') to refine matches of ''signed'' and ''unsigned'' integers.]]You should have noticed that the command worked correctly this time because you used the '''egrep''' command.<br><br>'''NOTE:''' With extended regular expressions, the '''?''' symbol can be used to represent the '''{0,1}''' repetition symbols and the '''+''' symbol can be used to represent the '''{1,}''' repetition symbols<br><br># Issue the following Linux pipeline command using the repetition shortcuts <span style="font-weight:bold;font-family:courier;">"+"</span> and <span style="font-weight:bold;font-family:courier;">"?"</span>:<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep "^[+-]?[0-9]+$" numbers2.dat | tee better-number2.txt</span><br><br>You should have seen the '''same results''', but less typing was required.<br><br># Issue the following Linux pipeline command to display '''signed''', '''unsigned''', '''whole''', and '''decimal''' numbers:<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep "^[+-]{0,1}[0-9]{1,}[.]{0,1}[0-9]*$" numbers2.dat | tee better-number3.txt</span><br><br>Were all signed and unsigned intergers and decimal numbers displayed?<br><br># Issue the follwoing command to check that you correctly issued<br>those ''Linux pipeline commands'': <br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week9-check-2</span><br><br>If you encounter errors, then view the feedback to make corrections, and then re-run the checking script.<br>If you receive a congratulation message that there are no errors, then proceed with this tutorial.<br><br>You can also use extended regular expression symbols for '''grouping'''.<br>For example, you can search for repetitions of GROUPS of characters (like a word)<br>as opposed to just a single character or a GROUP of numbers as opposed to a single digit.<br><br># Issue the following linux pipeline command to copy another data file called '''words.dat''':<br><span style="color:blue;font-weight:bold;font-family:courier;">cp ~uli101/tutorialfiles/words.dat ~/</span><br><br># View the contents of the '''words.dat''' file using the '''more''' command and quickly view the contents of this file.<br>Within this file, you should notice some lines that contain repetitions of words. When finished, exit the more command.<br><br># Issue the following linux pipeline command to display '''two or more occurrences''' of the word "the":<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep -i "(the){2,}" words.dat | tee word-search1.txt more</span><br><br>'''NOTE: No output is displayed! Why?'''<br><br>This is due to the fact that a <u>space</u> should be included at the end of the word "'''the'''".<br>Usually words are separated by spaces; therefore, there were no matches since there were not occurrences<br>of "thethe" as opposed to "'''the the'''" (i.e. no space after repetition of the pattern).<br><br># Reissue the previous pipeline command with the word the followed by a '''space''' within the brackets:<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep -i "(the ){2,}" words.dat | tee word-search2.txt</span><br><br>[[Image:eregexps-3.png|thumb|right|330px|Using '''extended''' regular expression symbols (such as '''grouping''') to refine matches of repetition of '''words''' (as opposed to ''characters'').]]The <span style="font-weight:bold;font-family:courier;">"|"</span> (or) symbol (same symbol as "pipe") can be used within the grouping symbols to allow matching of additional groups of characters.<br>Again, it is important to follow the character groupings with the space character<br><br># Issue the following linux pipeline command to search for '''two or more occurrences''' of the word "'''the '''" <u>or</u> '''two or more occurrences''' of the word "'''and '''":<br><span style="color:blue;font-weight:bold;font-family:courier;">egrep -i "(the |and ){2,}" words.dat | tee word-search3.txt</span><br><br># Issue the following Linux command to check that you correctly issued<br>those ''Linux pipeline commands'' using the '''tee''' command to create those text files:<br><span style="color:blue;font-weight:bold;font-family:courier;">~uli101/week9-check-3</span><br><br>If you encounter errors, then view the feedback to make corrections, and then re-run the checking script.<br>If you receive a congratulation message that there are no errors, then proceed with this tutorial.<br><br>Let's issue a Linux '''pipeline''' command using the '''egrep''' command as a '''filter'''<br>using <u>both</u> '''complex''' and '''extended''' regular expressions.<br><br># Issue the following Linux pipeline command:<br><span style="color:blue;font-weight:bold;font-family:courier;">ls | egrep "[a-z]{1,}.*[0-9]"</span><br><br>What did this Linux pipeline command display?<br><br>: The '''grep''' and '''egrep''' Linux commands are NOT the only Linux commands that use regular expressions.<br>In the next investigation, you will apply regular expressions to a number of Linux commands<br>that you already learned in this course.

In the next investigation, you will ... =: You can proceed to INVESTIGATION 3: OTHER COMMANDS THAT USE REGULAR EXPRESSIONS =<br> In this section, you will learn how to ...<br>

# Make certain that you are located in your '''~/regexps''' directory on your ''Matrix'' account.<br><br># Let's look at using regular expressions with the '''man''' command.<br>Issue the following linux command :<br><span style="color:blue;font-weight:bold;font-family:courier;">man ls</span><br><br>[[Image:other-re-1.png|thumb|right|300px|Entering '''/sort''' in the '''man''' command can search for the string "'''sort'''".]]# We want to search for an option that can sort the file listing.<br>Type the following regular expression below and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">/sort</span><br><br>'''FYI:''' The '''grep''' and '''egrep''' Linux commands contain the regular expressions within quotes, but '''most''' other Linux commands specify regular expressions using<br>'''forward slashes''' (e.g. <span style="font-weight:bold;font-family:courier;">/regular expression</span> &nbsp; or &nbsp; <span style="font-weight:bold;font-family:courier;">/regular expression/</span>).<br><br># Scroll throughout the man pages for the ls command to view matches for the pattern "'''sort'''"<br>(You can press '''SPACE''' or key combination '''alt-b''' to move forward and backwards one screen respectively).<br><br># Press the letter <span style="color:blue;font-weight:bold;font-family:courier;">q</span> to '''exit''' the ''man'' pages for '''ls'''.<br><br>Let's use regular expressions with the '''less''' command.<br><br># Issue the following Linux command to copy another data file called '''large-file.txt''':<br><span style="color:blue;font-weight:bold;font-family:courier;">cp ~uli101/tutorialfiles/large-file.txt ~/</span><br><br>[[Image:other-re-2.png|thumb|right|300px|Entering '''/uli101''' in the '''less''' command can display all matches of "'''uli101'''" throughout the text file.]]# Issue the following Linux command to view the contents of the '''large-file.txt''':<br><span style="color:blue;font-weight:bold;font-family:courier;">less large-file.txt</span><br><br>#We want to search for a pattern '''uli101''' within this text file.<br>Type the following regular expression and press ENTER:<br><span style="color:blue;font-weight:bold;font-family:courier;">/uli101</span><br><br>You should see the pattern "uli101" throughout the text file.<br><br># Press the letter <span style="color:blue;font-weight:bold;font-family:courier;">q</span> to exit the '''less''' command.<br><br># Try the same search techniques with the '''more''' command.<br><br>Does it work the same for the ''less'' command?<br><br>[[Image:other-re-3.png|thumb|right|300px|Entering '''/uli101''' in the '''vi''' command can search for the string "'''uli101'''".]]Let's learn how to perform a simple '''search and replace''' within the '''vi''' utility<br>by using regular expressions.<br><br># Issue the following Linux command to edit the '''large-file.txt''' file:<br><span style="color:blue;font-weight:bold;font-family:courier;">vi large-file.txt</span><br><br>Let's first perform a simple search within this text file.<br><br># Press the '''ESC''' key to make certain you are in '''COMMAND''' mode.<br><br># Type the following and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">/uli101</span><br><br>You should notice the pattern "'''uli101'''" highlighted for ALL occurrences in this text file.<br><br>Let's '''search''' for the '''uli101''' pattern, and '''replace''' it in capitals (i.e '''ULI101''').<br><br>In vi, to issue a command, you need to enter '''LAST LINE''' MODE then issue a command.<br>Let's issue a command from '''LAST LINE''' MODE to search and replace '''uli101''' to '''ULI101'''.<br><br>[[Image:other-re-4.png|thumb|right|500px|In l'''ast line''' MODE in the '''vi''' text editor, issuing a command using regular expressions to convert '''uli101''' to '''ULI101'''.]]# Making certain that you are '''COMMAND''' MODE in vi,<br>type the following and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">:%s/uli101/ULI101/g</span><br><br>'''NOTE:''' The letter '''g''' after the replace regular expression represents "'''global'''" and will replace ALL occurrences of uli101 in the text document (as opposed to replacing the first occurrence for every line).<br><br># Type the following (in uppercase letters) and press '''ENTER''':<br><span style="color:blue;font-weight:bold;font-family:courier;">/ULI101</span><br><br>You should notice the pattern "'''ULI101'''" highlighted for ALL occurrences in this text file.<br><br># Navigate throughout the text file to confirm that ALL occurrences of '''uli101''' have been <u>replaced</u> with '''ULI101'''.<br><br># Save changes to your vi editing session and exit by typing the following and pressing ENTER:<br><span style="color:blue;font-weight:bold;font-family:courier;">:x</span><br><br>

https://ictwiki.cdot.senecacollege.ca/~murray.saululi101/uli101files/uli101_command_practice_9a.docx

'''Review QuestionsPart A:Display Results from Linux Commands using Simple &amp; Complex Regular Expressions'''

'''Part A: Display Results from Linux Commands using Regular Expressions''' Note the contents from the following tab-delimited file called '''~murray.saul/uli101/cars''':

Plym fury 77 73 2500chevy nova 79 60 3000 ford mustang 65 45 10003volvo gl 78 102 9850 ford ltd 83 15 10507 chevy nova 80 50 3503 fiat 600 65 115 450 honda accord 81 30 6000ford thundbd 84 10 17000toyota tercel 82 180 755chevy impala 65 85 1553ford bronco 83 25 9505

1. <span style="font-family:courier;font-weight:bold">grep plym ~murrayuli101/cars</span><br>2.saul<span style="font-family:courier;font-weight:bold">grep -i fury ~uli101/cars</span><br>3. <span style="font-family:courier;font-weight:bold">grep “^[m-z]” ~uli101/cars</span><br>4. <span style="font-family:courier;font-weight:bold">grep -i “^[m-z]” ~uli101/cars</span><br>5. <span style="font-family:courier;font-weight:bold">grep “3$” ~uli101/cars</span><br>6. <span style="font-family:courier;font-weight:bold">grep -i “c.*5$” ~uli101/cars</span><br>

7. Write a Linux command to display all lines in the file called '''~/text.txt''' that contains the pattern:the<br>8. Write a Linux command to display all lines in the file called '''~/text.txt''' that contains the word:the<br>9. Write a Linux command to display all lines in the file called '''~/text.txt''' that begin with a number.<br>10. Write a Linux command to display all lines in the file called '''~/text.txt''' that end with a letter(either upper or lowercase).<br>11. Write a Linux command to display all lines in the file called '''~/text.txt''' that begin and end with a number.<br>12. Write a Linux command to display all lines in the file called '''~/text.txt''' that contains exactly 3characters that can be anything.<br>13. grep “^[m-z]” Write a Linux command to display all lines in the file called '''~murray/text.saultxt''' that contains exactly 3 numbers.<br>14. Write a Linux command to display all lines in the file called '''~/uli101/carstext.txt''' that contains 1 or more “C” characters.<br>

5. grep “3$” Note the contents from the following tab-delimited file called '''~murray.saul/uli101/carsnumbers.txt''':

61. <span style="font-family:courier;font-weight:bold">grep "^[-i “c+]" ~uli101/numbers.txt</span><br>2.<span style="font-family:courier;font-weight:bold">grep "^[-+]*.[0-9]" ~uli101/numbers.txt</span><br>3. <span style="font-family:courier;font-weight:bold">grep "^[+-]?[0-9]" ~uli101/numbers.txt</span><br> &nbsp; &nbsp;(Why?)<br>4. <span style="font-family:courier;font-weight:bold">egrep "^[+-]?[0-9]" ~uli101/numbers.txt</span><br>5. <span style="font-family:courier;font-weight:bold">egrep "^[+-]?[0-9]+$” " ~murrayuli101/numbers.saultxt</span><br>6. <span style="font-family:courier;font-weight:bold">egrep "^[+-]?[0-9]+[.]?[0-9]+$" ~uli101/cars numbers.txt</span><br>

 7. Write a single Linux command to display all lines in the file called ~/text.txt that contains the pattern:the   8. Write a Linux command to display all lines in the file called ~/text.txt that contains perform the word:specified tasks for each of the   9. Write a Linux command to display all lines in the file called ~/text.txt that begin with a number.    10. Write a Linux command to display all lines in the file called ~/text.txt that end with a letter (either upper or lowercase).    11. Write a Linux command to display all lines in the file called ~/text.txt that begin and end with a number.     12. Write a Linux command to display all lines in the file called ~/text.txt that contains exactly 3 characters that can be anythingfollowing questions.  

138. Write a Linux command to display all lines in the file called '''~/textdata.txt ''' that contains exactly ends with 3 numbers.or more occurrences of the number 6

If you wish additional practice using extended regular expressions, here is a link to another MS Word documentLicense:LGPL version 3Link: https://ictwww.senecacollege.ca/~murraygnu.saulorg/uli101licenses/uli101_command_practice_9blgpl.docxhtml